The present invention relates to a method and an apparatus processing a color video signal, and more precisely, a method and an apparatus for generating information for copy protection with regard to a video tape recorder (VTR) or a video cassette recorder (VCR) with which a video program is copied.
Recently, quite a few methods have been proposed and carried out for protecting or prohibiting a VTR or VCR from copying a video program on a video tape.
For example, U.S. Pat. No. 4,577,216 teaches the following method:
Modify a color television (TV) signal so that the modified signal reproduces a normal picture when a conventional TV receiver receives the modified signal; however, when the modified signal is recorded in a video tape and playbacked, color noises emerge to turn the color picture unpleasant, whereby restraining anyone from copying a video program on a video tape not any more.
The above method is detailed as follows:
Modify a color burst signal for color video signal through phase modulation with noises or an appropriate signals. In the conventional color TV receiver, the modified signal does not influence the regeneration circuit of color subcarrier although the burst signal is phase-modulated. However, when a video tape including the modified signal is playbacked in a VTR or VCR, the VTR or VCR responds the phase-modulated color burst signal and changes the phase of chrominance signal, as a result, unpleasant color noises emerge in pictures when the video tape is playbacked and thus it is expected that anyone is restrained from copying a video program not any more.
Yet, in actual, the phase-modulated color burst signal sometimes influences the regeneration circuit for color subcarrier of the conventional color TV receiver. When a video with a high degree of color saturation is displayed in particular, unpleasant striped color noises sometimes appear in the screen.
Properly speaking, the copy protecting method should be effective only to the playback function of a VTR or VCR, and should not influence the conventional color TV receiver. Thus the above phenomenon is a problem to be solved.